Cal Fire spokesman Daniel Berlant said that the Butts Canyon Road area and Berryessa Estates in Pope Valley are under mandatory evacuations.

Mandatory evacuations are also in effect along state Highway 29 as far south as Tubbs Lane, just north of Calistoga, Berlant said.

Calistoga residents have not been advised to evacuate, he said.

Emergency officials have set up road closures at Howell Mountain Road at Pope Valley Road and Ink Grade Road at White Cottage Road North, officials with the Napa County Office of Emergency Services tweeted at 9:53 p.m.

An evacuation center has been set up at the Napa County Fairgrounds in Calistoga, Lake County emergency officials said.

Berlant said a combination of wind and the “tinder dry” grass, brush and trees caused the fire to spread so rapidly:

“The dry conditions are playing a huge role,.

The winds are not extreme, at about 20 mph, with gusts up to 30 mph, he said.

The fire has been burning so rapidly it has challenged firefighters ability to notify people of the danger. That’s why such a large area is under orders to evacuate, he said.

“But we need the public’s help,” he said. Even if people live in the general area of the fire, “be prepared.”